If your loved one takes more than one type of medication, it’s important for you both to know about the basics of drug interaction.

Understanding drug interaction is particularly important for caregivers, because many care recipients take multiple medications. This is especially true with elderly care recipients who consume almost 40 percent of all over-the-counter drugs and 30 percent of all prescription drugs.

A drug interaction is a change in the effect of a drug when it is taken with another drug, food, or substance. Because medications are prescribed to treat specific illnesses or symptoms, such changes mean that the drug is no longer effective, and in many cases, it could become very dangerous.

Drugs interact in a few ways, including:

By increasing or decreasing drug absorption from the stomach and intestines

By increasing or decreasing the rate at which the body breaks drugs down in the liver

By increasing or decreasing the rate at which the drugs are excreted from the body by the kidneys

By causing competing actions in the body

Your loved one is at a greater risk for experiencing a drug interaction if he or she:

Is dehydrated

Is female

Is overweight

Takes multiple drugs

Is very young or old

Has congestive heart failure

Has had a previous drug interaction

Has liver or kidney damage

Has low or high blood pressure

Has multiple diseases

Has poor nutrition

If your loved one falls into any of these at-risk categories, or if you have additional concerns or questions about a possible drug interaction, contact your loved one’s pharmacist or doctor. You can also help protect your loved one by following these simple steps:

Make sure that the doctor knows about—and is kept updated on—all medications taken by your loved one (herbal medications, home remedies, over-the-counter drugs, and prescriptions drugs).

Once a year, have your loved one’s doctor or pharmacist review all of his or her medications.

Ask the doctor or pharmacist questions about anything that you don’t understand.

Always go to the same pharmacy to fill your loved one’s prescriptions.